Structure, optical device, magnetic device, magnetic recording medium and manufacturing method thereof

ABSTRACT

A nano structure having pore array structures in which a plurality of periodic arrays are formed adjacent to one another and a method of manufacturing the nano structure are provided. A nano structure having periodic array structures of pores formed in an anodized oxide film with a plurality of types of the periodic array structures arranged adjacent to one another is provided. Furthermore, a method of manufacturing a nano structure in which a plurality of periodic array structures formed in an anodized oxide film having different periods are arranged adjacent to one another, including (1) a step of forming pore starting points made up of a plurality of types of periodic arrays on the surface of a substrate comprised of aluminum as a principal component and (2) a step of anodizing the substrate simultaneously at the same anodization voltage is provided.

TECHNICAL FIELD

The present invention relates to a structure having concavo-convexstructures on the order of nanometers arranged at intervals on the scaleof nanometers (hereinafter also referred to as a “nano structure”), anoptical device, a magnetic device, a magnetic recording medium, and amethod of manufacturing the structure.

BACKGROUND ART

As a technology of forming a nanostructure or microstructures on thesurface of an object, a technology of forming pores of several hundrednm or less in size using an anodization for a film or substratecomprised of aluminum as a principal component rather than a lithographytechnology using light rays or electron beams is conventionally known.

The anodization method is a method applying an electric field to asubstrate comprised of aluminum as a principal component as an anode inan acid bath oxidation and a dissolution phenomenon and form pores onthe surface of the substrate. These pores are formed straightforward inthe vertical direction starting from the surface of the substrate, havea high aspect ratio and also have excellent uniformity in diameters oftheir cross sections. Furthermore, it is possible to control thediameters and spacing of pores by adjusting a current and/or voltageduring anodization and control the thickness of an oxide film and depthof pores by controlling the duration of anodization, to a certainextent.

The positions of pores formed using this technique are random, but atechnique for obtaining regularly arrayed pore structures is proposed inrecent years. This technique forms regularly arrayed concave structureson the surface of a substrate comprised of aluminum as a principalcomponent using an optical lithography and imprint lithography, etc.,and conducts anodization using these structures as starting points ofpores (U.S. Pat. No. 6,139,713).

There are proposals on various applications focused on a specificgeometric structure of this anode alumina and detailed explanations aregiven by Masuda et al.

Examples of this include an application for a film which takes advantageof wear resistance and insulating properties of an anodized oxide filmand an application for a filter with a film peeled off. Attempts arealso made using a technology of filling pores with metal, semiconductoror magnetic substance or replica technology of pores for variousapplications including coloration, magnetic recording medium, ELlight-emitting device, electrochromic device, optical device, solarcell, gas sensor, etc. Moreover, a wide variety of applications such asquantum effect devices such as quantum wire and MIM device, molecularsensor using pores as a chemical reaction field, etc., are expected.

A longitudinal recording system, which is the current mainstream ofmagnetic recording media, becomes more liable to demagnetization as therecording density increases and limitation of its recording density ispointed out. As an alternative technology, there is a proposal on aperpendicular magnetic recording system which records data bymagnetizing a recording medium in the vertical (film thickness)direction. According to this system, the demagnetizing field decreasesand a more stable state is produced as the recording density increasesas opposed to the conventional longitudinal recording system.Furthermore, this system can also increase the thickness of therecording film compared to the longitudinal recording system, andtherefore it is said to be resistant to thermal fluctuations inprinciple. There is a proposal on an application of an anodized oxidefilm for a perpendicular magnetic recording medium using such aperpendicular magnetic recording system (Japanese Patent ApplicationLaid-Open No. H11-224422).

The above described nano structure is generally formed using alithography technology and etching technology, but using suchtechniques, it is extremely difficult to form a high aspect structurewhich is realized by the anodization method.

Furthermore, the above described magnetic recording medium isdisk-shaped and the rotator when information is recorded or reproducedis subject to fine vibration or eccentricity, which prevents recordedtracks from becoming concentric, producing position errors of the headand tracks. Similar position errors are also produced by deformation dueto expansion of the disk caused by a thermal distribution in theapparatus. Therefore, the recording area is divided into data areas forrecording information and servo areas for detecting track positions andpositions are corrected while the head is detecting position informationof tracks, but patterned media which are being developed in recent yearshave a problem as to how to construct servo areas.

The present invention has been implemented in view of the abovedescribed problems and it is an object of the present invention toimprove the above described points and provide a nano structure havingpore array structures in which a plurality of periodic arrays are formedadjacent to one another.

Furthermore, the present invention also provides a method ofmanufacturing a nano structure in which a plurality of periodic arraysare formed adjacent to one another in a short time by applyinganodization to pore starting points formed on a substrate all togetherat one anodization voltage.

Furthermore, the present invention also provides an optical device withthe pores having the nano structure filled with a dielectric having adielectric constant.

Furthermore, the present invention also provides an optical device withthe pores having the nano structure filled with a light-emittingmaterial.

Furthermore, the present invention also provides a magnetic device withthe pores having the nano structure filled with a magnetic material.

Furthermore, the present invention also provides a magnetic recordingmedium capable of constructing effective servo areas by filling poreshaving the nano structure with magnetic substance and providing aplurality of periodic array structures in the servo areas.

DISCLOSURE OF INVENTION

That is, the present invention is a structure comprising a first areahaving a plurality of pores which have only a first period and a secondarea having a plurality of pores which have only a second period,characterized in that the first area and the second area share aplurality of pores.

Furthermore, the present invention is a structure comprising periodicarray structures of pores formed in an anodized oxide film,characterized in that a plurality of types of periodic array structuresare arranged adjacent to one another.

The above described plurality of types of periodic array structures arepreferably arranged adjacent to one another and there are preferably atleast two pores in the shared region which constitutes the boundarythereof.

The above described plurality of types of periodic array structurespreferably have at least one pore in addition to the pores in the sharedregion.

The above described plurality of types of periodic array structures eachpreferably have equal distances between first proximate pores or havethe distance between first proximate pores on one side equal to thedistance between second proximate pores on the other side or have equaldistances between second proximate pores.

The distance between the most proximate pores of the above describedplurality of types of periodic array structures is preferably 0.75B to1.5B (where B is a numerical value [nm] included within the rangebetween a maximum value and a minimum value of the distance between themost proximate pores of the above described plurality of types ofperiodic array structures).

According to an aspect of the present invention, there is provided astructure comprising: a first area comprising a plurality of pores whichhave a first period; and a second area comprising a plurality of poreswhich have a second period, wherein the first area and the second areaown a plurality of pores in common.

According to another aspect of the present invention, there is provideda structure comprising a plurality of pore groups having a periodicarray structure formed in an anodization film, wherein the pore groupsis arranged adjacent to at least any one of the pore groups.

In the above structure, the pore groups are arranged adjacent to oneanother by owning at least two pores in common. Each of the pore groupsmay comprise pores not owned in common. Alternatively, the periodicarray structure have a period different from the period of the adjacentpore group.

In the above structure, the distance between the most proximate pores ofthe plurality of types of periodic array structures are 0.75B to 1.5B(where B is a numerical value [nm] included within the range between amaximum value and a minimum value of the distance between the mostproximate pores included in the plurality of types of periodic arraystructures).

In the above structure, the distance between the pores making up unitlattices of the plurality of types of periodic array structures areprefarably a to 2a (where a is the distance [nm] between the mostproximate pores included in the plurality of types of periodic arraystructures)

The above described plurality of types of periodic array structures ispreferably a rectangular lattice, tetragonal lattice, hexagonal lattice,graphite-shaped lattice or parallelogram lattice.

The above described anodized oxide film is preferably comprised ofaluminum as a principal component.

At least one of the above described pores preferably includes a filler.

The above described filler is preferably a dielectric having adielectric constant different from that of the above described anodizedoxide film, semiconductor, magnetic material or light-emitting material.

Furthermore, the present invention is an optical device characterized inthat the pores of the above described structure are filled with adielectric having dielectric constant different from that of the abovedescribed anodized oxide film.

Furthermore, the present invention is a light-emitting devicecharacterized in that the pores of the above described structure arefilled with a light-emitting material.

Furthermore, the present invention is a magnetic device characterized inthat the pores of the above described structure are filled with amagnetic material.

Furthermore, the present invention is a magnetic recording mediumcomprising a data area where pores filled with the above describedmagnetic material record information and a servo area where trackpositions are detected, characterized in that the structure made up ofsimple periodic arrays of the above described pores differs between thedata area and the servo area.

At least one pore in the above described servo area is preferablyshifted by half a period with respect to the period of poresperpendicular to the track direction of the data area.

The above described servo area is preferably constructed of at least twotypes of periodic array structures.

Furthermore, the present invention is a method of manufacturing astructure in which a plurality of pore periodic array structures formedin an anodized oxide film having different periods are arranged adjacentto one another, comprising (1) a step of forming pore starting pointsmade up of a plurality of types of periodic arrays on the surface of asubstrate comprised of aluminum as a principal component and (2) a stepof anodizing the above described substrate simultaneously at the sameanodization voltage.

The plurality of periodic array structures having different periods arepreferably arranged adjacent to one another and there are at least twopores in the shared region which is the boundary thereof.

The plurality of periodic array structures having different periodspreferably have at least one pore in addition to the pores in the abovedescribed shared region.

A voltage applied during anodization of the structure of the abovedescribed plurality of periodic arrays is preferably A [V] (B [nm]=A[V]/2.5 [V/nm], where B is a numerical value included within the rangebetween a maximum value and a minimum value of the distance between themost proximate pores included in the above described plurality of typesof periodic array structures).

The above described step (1) is preferably formed by an opticallithography, X-ray lithography, electron beam lithography, ion beamlithography, imprint lithography or scanning prove microscopy (SPM)lithography.

Furthermore, the present invention is a structure characterized by beingmanufactured using the above described method.

The present invention will be explained in detail below.

The structure of the present invention includes a nano structure as atypical example thereof, and therefore the nano structure will beexplained.

The nano structure according to the present invention is a structurewith a periodic array of pores formed in an anodized oxide film andarray structures with a plurality of types of periods are arrangedadjacent to one another.

The pores according to the present invention include pores filled with amaterial after those pores are formed.

The method of manufacturing the nano structure of the present inventionconsists of forming desired pore starting points made up of a pluralityof periodic array structures on the surface of a substrate comprised ofaluminum as a principal component using a lithographic method, etc., andapplying anodization to these pore starting points at an appropriateapplied voltage. The structure formed with the distance between mostproximate pores of the periodic array structures limited to 0.75B to1.5B (where B is a numerical value [nm] included within the rangebetween a maximum value and a minimum value of the distance between themost proximate pores of the plurality of types of periodic arraystructures) allows a batch of anodization at a single voltage. Here, thenano structure refers to a structure having a shape variation orcomposition variation with the period of the concavo-convex structuresbeing 1 μm or less.

The nano structure of the present invention is a structure with aperiodic array of pores formed in an anodized oxide film and is astructure in which a plurality of periodic arrays having differentperiods are arranged adjacent to one another. Furthermore, there are atleast two pores in a shared region which is the boundary of the adjacentperiodic arrays and there is at least one pore in addition to the poresin the shared region. The distance between the most proximate pores ofthe periodic array structures is preferably 0.75B to 1.5B (where B is anumerical value included within the range between a maximum value and aminimum value of the plurality of periods). For example, when porestarting points made up of a hexagonal lattice having a period of 200 nmis subjected to anodization with an anodization voltage of 40 V applied,because 40 V×2.5 [m/V]=100 nm, 40 V corresponds to the anodizationvoltage of a period of 100 nm, and therefore pores are also formed inareas where no pore starting points exist. Therefore, to perform a batchof anodization on array structures of a plurality of types of periods,the smaller the distance between most proximate pores of a plurality oftypes, the better, and the probability that pores may also be formedfrom places other than the pore starting points increases when thedistance exceeds the range of 0.75B to 1.5B. For these reasons, thevoltage in a batch of anodization (step (2)) is preferably calculatedfrom the most proximate distances which are most numerous in thestructure.

FIG. 1 is a plan view illustrating the nano structure of the presentinvention. For example, using a technique such as an opticallithography, pore starting points 1 of a plurality of periodic arraystructures 6 made up of a hexagonal lattice area 3, a rectangularlattice area 4 and a graphite-shaped lattice area 5 are formed on thesurface of a substrate as shown in FIG. 1. At this time, periodicstructures such that pores 2 located on the boundaries among a pluralityof periodic array structures 6 are shared are arranged continuously. Anormal anodization voltage is uniquely determined depending on theperiod of pores, but when pore starting points are formed, it ispossible to obtain pores having the same period as the starting pointperiod regardless of a certain degree of voltage shifts. That is, withpore starting points whose period varies only slightly, it is possibleto actually form regularly arrayed high aspect pores in a short timewithout producing any disorder of arrays. As the method of formingstarting points of pore formation, it is also possible to actually formdents on the surface of a film to be subjected to anodization or maskareas other than starting points. Or it is also possible to form ananodization film on a substrate having projections and depressions withpredetermined periodicity and use projections and depressions reflectingthe projections and depressions of the base as starting points.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view illustrating a nano structure of the presentinvention;

FIGS. 2A, 2B and 2C are plan views illustrating the nano structure ofthe present invention;

FIG. 3 is a schematic view illustrating a nano structure according toEmbodiment 2 of the present invention; and

FIG. 4 is a perspective view illustrating a nano structure of accordingto Embodiment 3 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference now to the attached drawings, embodiments of the presentinvention will be explained in detail below. The same reference numeralswill denote the same parts in all drawings.

Embodiment 1

First, as step (2), concave structures having desired arrays are formedon the surface of a substrate on which an aluminum thin film is formedusing an electron beam direct drawing method and these are used as porestarting points. As shown in FIG. 1, the array of pore starting points 1consists of a hexagonal lattice area 3, a rectangular lattice area 4 anda graphite-shaped lattice area 5 affanged adjacent to one another andpores 2 on the boundary of the adjacent areas are shared by both areas.That is, the two adjacent areas share an away of pores with equalperiodicity on the boundary. Black bullets 1 in FIGS. 2A to 2C indicateprojected positions of pores on a plane of the hexagonal lattice area,rectangular lattice area and graphite-shaped lattice area in FIG. 1. InFIGS. 2A to 2C, a period 8 of the hexagonal lattice area 3 is 200 nm, aperiod 9 of the rectangular lattice area 4 in the Y direction is 200 nm,that of the X direction is 250 nm and the most proximate distance 10 ofthe graphite-shaped lattice area 5 is 200 nm. According to thisstructure, when B=200 nm that is minimum value in periods, the allowedperiodic array structures are in the range of 150 nm to 300 nm, theseare included in 0.75B to 1.5B.

Then, all the pore starting points formed in step (2) are subjected toanodization simultaneously at the same voltage. As the anodizationvoltage, a voltage [V] obtained by {basic period [nm]+2.5 [m/V]} isgenerally considered optimum. Since the most numerous most proximatedistance is 200 nm, if the basic period (anodization period) is assumedto be 200 nm, the anodization voltage becomes 80 V. When a substrate isimmersed in an aqueous solution of 0.3 mol/L phosphoric acid at 20° C.and anodization is applied using this as the anode with 80 V applied,then aluminum is oxidized and dissolved from the pore starting pointsand high aspect pores are formed.

Then, pore walls of aluminum oxide are dissolved in the aqueous solutionof phosphoric acid and pore diameters are thereby expanded andcontrolled. FIGS. 2A, 2B and 2C show pores after the pore diameters areexpanded. The shape of pore 7 a in the hexagonal lattice area issubstantially circular as shown in FIG. 2A, the shape of pore 7 b in therectangular lattice area is rectangular as shown in FIG. 2B and theshape of pore 7 c in the graphite-shaped lattice area is triangular withno pores formed from areas without pore starting points throughanodization under this condition, as shown in FIG. 2C.

Embodiment 2

As a magnetic device, pores with hexagonal lattice areas and rectangularlattice areas having the same period as that of Embodiment 1 which arerepeatedly arranged adjacent to one another are formed. FIG. 3 showsarrays of pores. The method of formion is the same as that inEmbodiment 1. Cobalt is charged into the pores formed by an electricplating method to convert the area to a magnetic recording area. In thismagnetic device, a direction 13 is regarded as the track orientation andthe magnetic device is used, divided into a servo area 11 and data area12. Some magnetic substance cell groups in the servo area are half aperiod shifted from the period of the magnetic substance cell groups inthe direction perpendicular to the track direction and this is effectivefor performing position control (called “off track”) of the head andtracks. This prevents information of the adjacent tracks from beingmistakenly reproduced or information from being overwritten on thealready recorded adjacent tracks. Reducing the servo area through thesearrays makes it possible to secure the data area and realize a muchhigher density. In FIG. 3, reference numeral 14 denotes pores in theshared region.

Embodiment 3

As a device, pores with hexaganol lattice areas arranged on both sidesof a rectangular lattice area formed. The method of formation is thesame as that of Embodiment 1 and then polystyrene with light-emittingpigment is charged into the pores. Since the photonic band structure ofthe rectangular lattice area is different from that of the hexagonallattice area, wavelengths which are easily guided vary depending ontheir respective structures. For this reason, when light wave whichpropagates through the rectangular lattice area but does not propagatethrough the hexagonal lattice area is introduced into the pores in therectangular lattice area in the vertical direction 16 (see FIG. 4) andif this structure is regarded as a light waveguide, the rectangularlattice area becomes a core and the hexagonal lattice area becomes acladding and light wave propagates with lower loss compared with anormal two-dimensional light waveguide. Filling arbitrary pores in thecore area with a light-emitting pigment makes it possible to excite andmake propagate light waves with different wavelengths and this isapplicable to an optical device. In FIG. 4, reference numeral 15 denotesa light-emitting material and 17 denotes a light-emitting direction.

As described above, the present invention can provide a nano structurehaving pore array structures in which a plurality of periodic arrays arearranged adjacent to one another.

Furthermore, the present invention can provide a method of manufacturinga nano structure in which a plurality of periodic arrays are formedadjacent to one another in a short time by applying anodization to porestarting points formed on a substrate all together at an anodizationvoltage.

Furthermore, the present invention can provide an optical device withthe pores having the nano structure filled with a dielectric having adielectric constant.

Furthermore, the present invention can provide a light-emitting devicewith the pores having the nano structure filled with a light-emittingmaterial.

Furthermore, the present invention can provide a magnetic device withthe pores having the nano structure filled with a magnetic material.

Furthermore, the present invention can provide a magnetic recordingmedium capable of constructing an effective servo area by filling thepores having the nano structure with magnetic substance and providing aplurality of periodic array structures in the servo area.

1. A structure comprising a first area including a plurality of poresarranged in a lattice structure that is one of (a) a hexagonal lattice,(b) a rectangular lattice, and (c) a graphite-shaped lattice, and asecond area including a plurality of pores arranged in a latticestructure that is a different one of (a), (b), and (c), wherein thefirst area and the second area share a plurality of pores at a boundaryof the lattice structure of the first area and the lattice structure ofthe second area, and wherein the first area's pore interval is the sameas the second area's pore interval.
 2. A structure comprising periodicaway structures of pores formed in an anodized oxide film, wherein aplurality of types of periodic away structures are arranged adjacent toone another including (i) a first structure that is one of (a) ahexagonal lattice, (b) a rectangular lattice, and (c) a graphite-shapedlattice, and (ii) a second structure that is a different one of (a),(b), and (c), wherein the first structure and the second structure havepores in common on a boundary therebetween, and wherein in an areaoccupied by the first structure and in an area occupied by the secondstructure, the pore interval is the same.
 3. The structure according toclaim 2, wherein the first structure and the second structure have atleast one pore in addition to the pores in common.
 4. The structureaccording to claim 2, wherein the first structure and the secondstructure each have equal distances between first proximate pores orhave the distance between first proximate pores on one side equal to thedistance between second proximate pores on the other side or have equaldistances between second proximate pores.
 5. The structure according toclaim 4, wherein the distance between the most proximate pores of eachof the first structure and the second structure is 150 nm to 300 nm. 6.The structure according to claim 2, wherein said anodized oxide film iscomprised of aluminum as a principal component.
 7. The structureaccording to claim 2, wherein at least one of said pores includes afiller.
 8. The structure according to claim 7, wherein said filler is(a) a dielectric having a dielectric constant different from that ofsaid anodized oxide film, (b) a semiconductor, (c) a magnetic material,or (d) a light-emitting material.
 9. An optical device wherein saidpores of the structure according to claim 2 are filled with a dielectrichaving a dielectric constant different from that of said anodized oxidefilm.
 10. A light-emitting device wherein said pores of the structureaccording to claim 2 are filled with a light-emitting material.
 11. Amagnetic device wherein said pores of the structure according to claim 2are filled with a magnetic material.
 12. A magnetic recording mediumcomprising: a data area where pores filled with magnetic material torecord information; and a servo area where track positions are detected,wherein said data area comprises pores arranged in a structure that isone of (a) a hexagonal lattice, (b) a rectangular lattice, and (c) agraphite-shaped lattice, wherein said servo area comprises poresarranged in a structure that is a different one of (a), (b), and (c),wherein said data area's structure and said servo area's structure havepores in common at a boundary therebetween, and wherein said data area'spore interval is the same as said servo area's pore interval.
 13. Themagnetic recording medium according to claim 12, wherein at least onepore in said servo area is shifted by half a period with respect to aperiod of pores perpendicular to the track direction in the data area.14. A magnetic recording medium according to claim 12, wherein saidservo area is constructed of at least two types of periodic arraystructures.
 15. A method of manufacturing a structure in which aplurality of pore periodic array structures formed in an anodized oxidefilm having different periods are arranged adjacent to one another, saidmethod comprising: (1) a step of forming pore starting points made up ofa plurality of types of periodic arrays on the surface of a substratecomprised of aluminum as a principal component; and (2) a step ofanodizing said substrate's pore starting points simultaneously at thesame anodization voltage, wherein the plurality of pore periodic arraystructures comprise (i) a first structure that is one of (a) a hexagonallattice, (b) a rectangular lattice, and (c) a graphite-shaped lattice,and (ii) a second structure that is a different one of (a), (b), and(c), wherein the first structure and the second structure have pores incommon on a boundary therebetween, and wherein in an area occupied bythe first structure and in an area occupied by the second structure, thepore interval is the same.
 16. The method of manufacturing a structureaccording to claim 15, wherein the first structure and the secondstructure have at least one pore in addition to the pores in common. 17.The method of manufacturing a structure according to claim 15, wherein avoltage applied during anodization of the structure of said plurality ofperiodic arrays is A volts, and wherein the following condition issatisfied: B=A/(2.5 volts/nanometer) where B is within the range betweena maximum value and a minimum value of the distance between the mostproximate pores included in said plurality of pore periodic array)structures.